MFC非客户区问号显示帮助文档

对于客户区域显示的文档可以通过ON_WM_SYSCOMMAND()消息进行处理

---

BEGIN_MESSAGE_MAP(CTestDialog, CDialog)
   ON_WM_SYSCOMMAND()
END_MESSAGE_MAP()

void CTestDialog::OnSysCommand(UINT nID, LPARAM lPram)
{
   if (nID == SC_CONTEXTHELP)
   {
      AfxMessageBox(_T("hello "));      
      return;
   }
   return __super::OnSysCommand(nID,lPram);
}

参考链接 https://docs.microsoft.com/zh-cn/cpp/mfc/reference/cwnd-class?view=vs-2019#onsyscommand